Registration of an anatomical image with a position-tracking system may be carried out in various medical applications.
For example, U.S. Patent Application Publication 2014/0037174, issued as U.S. Pat. No. 9,076,212 on Jul. 7, 2015, whose disclosure is incorporated herein by reference, describes a system that adaptively compensates for subject motion in real-time in an imaging system. An object orientation marker, preferably a retro-grate reflector (RGR), is placed on the head or other body organ of interest of a patient during a scan, such as an MRI scan. The marker makes it possible to measure the six degrees of freedom (x, y, and z-translations, and pitch, yaw, and roll), or “pose”, required to track motion of the organ of interest. This invention also provides for internal calibration and for co-registration over time of the scanner's and tracking system's reference frames to compensate for drift and other inaccuracies that may arise over time.
U.S. Pat. No. 7,014,461, whose disclosure is incorporated herein by reference, describes an apparatus for measuring a surface geometry of hard tissue covered by a layer of soft tissue, including a plurality of elements each having a tip adapted to penetrate said soft tissue and not substantially penetrate said hard tissue; a frame supporting movement of said elements, each along a path, such that a plurality of said tips, when positioned along the paths, define a surface; and at least one position sensor which generates a signal indicative of a tip position of at least one of said elements.
U.S. Pat. No. 5,636,255, whose disclosure is incorporated herein by reference, describes method and system for correlating accuracy of computer tomography (CT) image resolution. Small radio-opaque markers having a diameter less than one slice width of a CT scan are embedded in the object, such as a bony skeletal member, to be measured, the object is then CT scanned so that the radio-opaque markers appear in at two slices of the scan. The markers are also physically located by detecting them with a sensor, such as a positioning pointer.